The background of the invention will be discussed in two parts.
1. Field of the Invention
This invention relates to marking apparatus, and more particularly to apparatus for marking the location of conduits and the like embedded in concrete.
2. Description of the Prior Art
Locating subterranean or subsurface pipes, conduits, outlet boxes and the like has presented a major problem when repair or replacement is required. Attempts have been made to provide marking of some sort as a means for enabling ready detection of the location of the pipes or conduits.
Various attempts at marking and/or locating of subsurface or subterranean pipes or conduits exist in the prior art. One such apparatus is shown and described in U.S. Pat. No. 3,115,861, entitled "Locating Elements of Construction Beneath the Surface of Earth Soils", which issued on Dec. 31, 1963 to Allen, the apparatus therein including a frangible layer buried in the earth at a spaced vertical distance above the pipe, so that excavation thereafter will reveal the frangible layer prior to the pipe as layers of earth are removed.
Another such apparatus is shown and described in U.S. Pat. No. 3,523,515, entitled "Above Surface Observed Marker Secured to Underground Utilities, etc., to Indicate Their Depth and Direction", which issued to Brown on Aug. 11, 1970, such patent showing a marker device for underground electrical cable, wherein the marker is attached to the cable within the trench, and thereafter during backfilling, means such as cross bracing are provided for supporting the marker in a vertical position while the trench is being filled.
Another attempt at resolving the problem of underground elements is shown in U.S. Pat. No. 3,533,243, entitled "Method of Laying Underground Pipes, Conduits and the Like so as to Make Their Presence Easily Detectable", which patent issued Oct. 13, 1970, to Suydam, the method including placing a dye or other colored indicant on the walls of the trench prior to backfilling.
U.S. Pat. No. 3,568,626, entitled "Identifying Means for Buried Utilities", issued to Southworth, Jr., on Mar. 9, 1971, and relates to a marked frangible strip member configured for placing above the buried utility element, with the strip including magnetic or radioactive portions which can be sensed above ground prior to excavation.
A warning tape including capsules of smoke releasing pellets is shown and described in U.S. Pat. No. 3,581,703, entitled "Warning Tape for Underground Installations", which issued to Hosack on June 1, 1971, the tape being positioned above the utility member for fracture or rupture at a depth less than the depth of the utility member.
Another above surface detectable strip or tape member is shown and described in U.S. Pat. No. 3,633,533, entitled "Location of Underground Utility Lines", which issued to Allen on Jan. 11, 1972, the tape including position being sensed electronically.
A bore hole method of pipe detection is shown and described in U.S. Pat. No. 3,653,050, entitled "Pipe Locator Method and Apparatus", which patent issued to Eggleston Jr. on Mar. 28, 1972.
A method of supporting a pipeline is shown and described in U.S. Pat. No. 3,747,355, entitled "Pipeline Support by Beams and Cables in Permafrost Areas", such patent issuing to Howard on Mar. 3, 1972.
U.S. Pat. No. 3,927,637, entitled "Positive Sub-surface Utility Line and the Like Indicator", issued to Sammaritano on Dec. 23, 1975, and shows and describes an apparatus including a measuring tape attached at one end to the buried device, such as a pipe or cable, the tape measure upper end being received within a housing, which is further provided with a pole and flag extending above the surface to indicate its location.
U.S. Pat. No. 4,654,639, entitled "Signaling Material and Method for Protecting Subterranean Structures" issued to De Courville on Mar. 31, 1987, and shows a signaling material in the form of a continuous support of a material having a low resistance to rupture, the rupture of the material during excavation providing visual indication of a structure therebeneath.
In the pouring of concrete to cover very large areas, such as in industrial and commercial buildings, conduits, such as electrical or communications ducts, or pipes for plumbing and gas, are buried in the concrete. The conduits are laid out in the proper locations, usually on a supporting subsurface, for the desired runs. For usage such as electrical, computer, telephone communications, etc., it is usually necessary that the location of the conduits or ducts, including such accessories as floor duct openings, junction boxes, electrical outlet boxes, etc., be known or marked to provide access after the concrete is poured. Such boxes or equipment which provide access to the electrical or communications wiring are referred to as "stub-outs", that is, these are termination ducts with boxes with covers which can be removed for adding electrical outlets or telephone outlets at certain locations,
In such concrete construction, the ducts may be round or rectangular in cross-section, and, in some manner, there must be a means for identifying the location of the access openings or stub-outs after the concrete has been poured. Such stub-outs are vertically disposed duct portions with upper open ends which are capped. During concrete pour, these capped ends are disposed some small distance below the surface of the finished floor and, after they are located, the thin layer of concrete covering is chipped away to provide access for removal of the cap and access to the electrical leads within the ducts.
One prior art method of marking the location of the stub-outs entails the use of threaded metallic members, such as screws, threadably affixed to some portion of the duct system, such as to flanges welded to the duct itself, or to covers attached to the openings of the boxes. The threaded members are unscrewed to a predetermined height above the duct or cover, generally to the intended elevation of the surface of the concrete floor.
One problem attendant to the use of these screw devices relates to the method of finishing the concrete floor. After the concrete is poured, or during the pour, an appropriate concrete finishing apparatus is utilized. One such apparatus is a gas motor powered "screed", which has a plurality of radially extending vanes or "trowel" members which rotate about a center axis. During screeding or finishing, these trowel members continually pass, in a circle, on the surface of the concrete. For any screw elevated too high, the result will be a bending or breakage of the screw, thus nullifying its intended purpose. On the other hand, if the screw lies below the concrete surface during finishing, its location thereafter will be hidden, thus requiring other means to find the screw, such as by use of a magnetic stud finder device or the like.
Accordingly, in accordance with an aspect of the invention, a feature is to provide a device and method for marking the location of conduits buried in concrete, which markers are relatively inexpensive and reliably located after finishing of the concrete.